This invention relates in general to machines for winding metal bands in a spiral arrangement and the products such machines produce and in particular to machines for forming flexible metal piping, and the piping produced by such machines.
The type of flexible metal piping disclosed in this application consists of a continuous metal band spirally wound in an arrangement wherein the leading portion of one winding interlocks with the leading portion of a subsequent winding one revolution later and this interlocking continues winding after winding. Where the trailing portion of one winding ends, the leading portion of the following, contiguous winding begins, although the concept of the beginning point and ending point is somewhat arbitrary due to the continuous nature of the metal band.
Concepts and features relating to such types of flexible metal piping and their fabricating apparata are disclosed by the following listed patents:
______________________________________ Patent No. Patentee Issue Date ______________________________________ 1,383,187 Brinkman et al. 6/28/21 1,596,215 Palmer 8/17/26 3,073,944 Yuter 1/15/63 1,617,583 Fentress et al. 2/15/27 2,944,337 Coleman 7/12/60 3,682,203 Foti et al. 8/08/72 ______________________________________
Brinkman et al. discloses an apparatus for making tubes wherein, by a series of dies and rollers, an initially flat metal band is continuously spirally wound on a mandrel thereby forming a plurality of interlocked convolutions.
Palmer discloses a method of making flexible metal tubes wherein, by a series of dies and rollers, an initially flat metal strip is spirally wound such that the adjacent overlying portion of each turn of the strip is anchored on adjacent turns thereby preventing circumferential twisting or unwinding of the strip. The interlocking shape is conventional and the tubing produced is of a continuous length for several feet.
Yuter discloses a method of welding and cutting helical formed tubing into sections, wherein the various windings of a flat metal band are joined together at their respective edges by a helical welded seam. The windings do not interlock with each other and it is felt that this reference has limited applicability to the subject application.
Fentress et al. discloses a method of and machine for manufacturing spiral metal tubes wherein the finished product does not rotate as it leaves the tube or spring forming tool with the result that a commercial tube or spring of any desired length may be produced by the machine, in which the power required to operate the machine is materially reduced.
Coleman discloses that flexible metal tubing, formed by winding an S-shaped strip, may be cut into lengths by cutting the strip and unscrewing the two pipe sections. However, the adjacent metal strip windings formed by the disclosed apparatus, do not interlock with each other and the nature of widthwise cutting disclosed in the patent would not be suitable, as disclosed, if the windings were interlocked with each other.
Foti et al. discloses a flexible metal hose of the type formed from a helical wound metal strip with the edges of adjacent helical turns deformed so as to interfold slidably so that adjacent helical turns slide axially against one another to permit the hose to be flexed along its axis.
It is noted that all of the above references which involve interlocked windings do not provide any means, other than the obvious method of hacksawing, by which to separate the continuous piping length into shorter lengths. Such a method, hacksawing, will result in 360.degree. (a full pipe circumference) of burrs on each free end which is cut and this condition is unacceptable for most applications. Consequently, a subsequent manual deburring operation must be performed if shorter pipe lengths are to be obtained from the longer continuous length. The only reference which suggests a reduced burr content way of obtaining individual pipe sections does not contemplate interlocked windings and thus would not be suitable for that particular style of flexible metal piping.
None of the references listed even remotely suggest means for conditionally segmenting a continuous length of piping, of interlocked windings, into a plurality of uniform, shorter sections wherein the severing of shorter sections from each other is performed by making a widthwise cut through a spirally wound metal band, thereby substantially reducing the burr content which would otherwise be present at each free end of these shorter sections of piping. Furthermore, none of the references listed suggest means for automatically controlling the length of, and uniformity of length between, these shorter sections of pipe. Nor do any of these references suggest the fabrication of a free (noninterlocked) winding as the means for conditionally segmenting the continuous length of piping into a plurality of shorter lengths.
The various shortcomings of these references, if overcome by incorporating novel features, would result in improved flexible metal piping and an improved method of manufacturing the same.